Along with technology development and increased demand for mobile devices, the demand for secondary batteries as an energy source is rapidly increasing. Among the secondary batteries, a lithium secondary battery having high energy density and voltage, long life cycle and low discharge rate is commercially available and widely used.
The lithium secondary battery includes a positive electrode having a positive electrode active material on at least one surface of a positive electrode current collector, a negative electrode having a negative electrode active material on at least one surface of a negative electrode current collector, and a separator interposed between the positive electrode and the negative electrode. In addition, as the interest in environmental issues grows, the market for high-capacity battery-driven devices such as electric vehicles and hybrid electric vehicles, which are capable of replacing vehicles using fossil fuel such as gasoline vehicles and diesel vehicles, one of main factors of air pollution, is growing, and accordingly the demand base for high capacity batteries is expanding. Thus, it is required to design a high capacity electrode for producing a lithium secondary battery with high energy density, high output and high discharge voltage as a power source of these devices.
For designing a high-loading electrode, the amount of a negative electrode active material is increased, which results in the increase of an electrode thickness. However, if the electrode thickness is increased, the binder may be irregularly distributed, which may deteriorate adhesion.
In addition, Si, its oxide or its alloy is being used to exhibit high capacity as a negative electrode active material. However, Si has a weak affinity with a binder, which may deteriorate the adhesion of the electrode, and may also degrade the life characteristic due to volume expansion.